Vertex color bake to texture causes wrong color margin
Give some margin

If you inspect closely your uv, you should se than there are no margin and some colors that are not exactly aligned with the uv grid.



This happens because the uv grid (which depend on the number of faces) has different size from the pixel grid (which depends on the baking texture size). You can try to match these with some calculations.... or you can re-unwrap the model in the following way:



set the smart uv margin tho a proper value (for a 1024x1024 tex I set 0.05) and than bake with a minumum bake margin of 1. Setting a margin allows a certain tollerance between color, avoiding overlaps and pixel-grid issues.